Sexual dimorphism relates to the visible differences between males and females within a determined species. Although most salamanders present some degree of sexual dimorphism, gender differences are more evident among newt species. Male individuals of banded or crested newts (Triturus) have dorsal crests and colorful tails, which they exhibit to the females during elaborate mating rituals.
Unlike other species of amphibians, such as frogs, all members of the order Caudata retain their tail throughout their lives. Newts often show flatter tails, in comparison to other salamander species, which have rounder and thicker tails. The paddletail newt (Pachytriton labiatus) is an Asian species with a long, flat tail. This newt fans its tail when communicating with other individuals.
Caudates are mainly found in the Americas, Asia and Europe, with about 30 percent of species living in North America. They prefer moist habitats, but are also found in dry climates, near river sources and ponds. Like other amphibians, caudates go through metamorphosis, living totally in the water during their early life cycle stages. While most salamanders are terrestrial when adults, returning to the water specially for breeding, a large number of newts live in the water throughout their lives.
Although the production of skin toxins for self defense is a characteristic of amphibians, newts are often more toxic than other salamanders. Some species of the genus Taricha, found in western North America, produce enough venom to kill an adult man, if ingested or in contact with an open wound. Taricha newts produce tetrodotoxin, a powerful venom also found in some frogs and the Japanese fugu fish. Tetrodotoxin from the eggs of Taricha newts is more toxic than other chemical compounds found in the skin of salamanders.